The subject matter disclosed herein relates to cooling holes and, more specifically, to modifying cooling holes for turbine components.
In gas turbine engines, such as aircraft engines or heavy duty gas turbines for example, air is drawn into the front of the engine, compressed by a shaft-mounted rotary-type compressor, and mixed with fuel. The mixture is burned, and the hot exhaust gases are passed through a turbine mounted on a shaft. The flow of gas turns the turbine, which turns the shaft and drives the compressor and fan. The hot exhaust gases flow from the back of the engine, driving it and the aircraft forward.
During operation of gas turbine engines, the temperatures of combustion gases may exceed 3,000° F., considerably higher than the melting temperatures of the metal parts of the engine which are in contact with these gases. Operation of these engines at gas temperatures that are above the metal part melting temperatures is a well-established art, and depends in part on supplying a cooling air to the outer surfaces of the metal parts through various methods. The metal parts of these engines that are particularly subject to high temperatures, and thus require particular attention with respect to cooling, are the metal parts forming combustors and parts located aft of the combustor, in the so-called “hot gas path”. For example, the operating temperatures can be partially regulated by using passageways such as cooling holes incorporated into some engine components such as buckets.
Superalloys, such as precipitation-hardenable Ni-based superalloys, or Co-based superalloys, can be used for turbine components to help withstand higher operating temperatures. However, the modification of these materials, particularly around cooling holes (e.g., proximate the tip of a bucket), may also require significant resources such as for properly preheating and/or cooling weld repair sites, removing original material, building up new material, and finishing any final surfaces into compliance ranges. As a result, modifying cooling holes through welding/brazing can require additional resources and time to allow for sufficient joining of additional material.
Accordingly, alternative methods for modifying cooling holes would be welcome in the art.